CVE-2023-28767 in ATP
Summary
by MITRE • 07/17/2023
The configuration parser fails to sanitize user-controlled input in the Zyxel ATP series firmware versions 5.10 through 5.36, USG FLEX series firmware versions 5.00 through 5.36, USG FLEX 50(W) series firmware versions 5.10 through 5.36,
USG20(W)-VPN series firmware versions 5.10 through 5.36, and VPN series firmware versions 5.00 through 5.36. An unauthenticated, LAN-based attacker could leverage the vulnerability to inject some operating system (OS) commands into the device configuration data on an affected device when the cloud management mode is enabled.
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Analysis
by VulDB Data Team • 07/18/2023
The vulnerability identified as CVE-2023-28767 represents a critical command injection flaw within the configuration parser of Zyxel network security appliances. This weakness affects multiple product lines including ATP series, USG FLEX series, USG FLEX 50(W) series, USG20(W)-VPN series, and VPN series devices. The vulnerability exists in firmware versions ranging from 5.10 through 5.36 for most affected models, with the USG20(W)-VPN series and VPN series supporting versions 5.00 through 5.36. The flaw manifests specifically when the cloud management mode is enabled, creating a dangerous attack vector for unauthenticated LAN-based adversaries.
The technical implementation of this vulnerability stems from insufficient input sanitization within the device's configuration parsing mechanism. When user-controlled data is processed through the configuration parser without proper validation or sanitization, malicious actors can inject OS commands that will be executed within the device's operating system context. This represents a classic command injection vulnerability that falls under CWE-77, which specifically addresses the improper neutralization of special elements used in commands. The flaw allows attackers to execute arbitrary commands with the privileges of the device's configuration process, potentially enabling full system compromise.
The operational impact of this vulnerability is severe for organizations relying on Zyxel security appliances in their network infrastructure. An unauthenticated attacker positioned on the local network can exploit this weakness to gain unauthorized access to device configuration data and potentially execute malicious commands. When cloud management mode is enabled, the attack surface expands beyond local network boundaries, as the vulnerability can be leveraged to inject commands that may persist across device reboots or configuration changes. This could lead to persistent backdoors, data exfiltration, network disruption, or complete device compromise. The vulnerability affects critical network security infrastructure, making it particularly dangerous for enterprise environments where these devices serve as primary security controls.
Mitigation strategies for CVE-2023-28767 should prioritize immediate firmware updates from Zyxel to address the root cause of the command injection vulnerability. Organizations should also implement network segmentation to limit access to affected devices and disable cloud management features when not required. Network monitoring should be enhanced to detect unusual command execution patterns or configuration changes that might indicate exploitation attempts. Security teams should conduct comprehensive vulnerability assessments across all affected Zyxel product lines and consider implementing intrusion detection systems specifically tuned to identify command injection attempts targeting network infrastructure devices. Additionally, organizations should review their network access controls and ensure that only authorized personnel can access device configuration interfaces, as the vulnerability does not require authentication from the local network perspective. This vulnerability aligns with ATT&CK technique T1059.001 for command and scripting interpreter and T1566.001 for credential access through social engineering, though the primary attack vector operates through the configuration parser rather than traditional credential theft methods.